The 5770 is nearly as fast as the 4870 and 260http://www.tomshardware.com/reviews/best-graphics-card,2464-4.html
If you want best performance, the 4870 or 260 is the way to go....which one very much depends on what titles are involved. Keep in mind 2 years from now you may need to upgrade to a DX11 card if DX11 becomes "the enxt big thing".
If you want to future proof as much as possible, get the 5770 which is DX11
If you want PhysX, 260 is only choice.http://www.tomshardware.com/reviews/batman-arkham-asylum,2465-11.html